1. Field of the Invention
The present invention relates to a projection exposure apparatus for exposing/transferring fine patterns on a substrate, which apparatus is used for the manufacture of, e.g., semiconductor elements such as LSIs.
2. Related Background Art
A lithographic process including transfer and exposure steps for a predetermined pattern is applied to the manufacturing process for semiconductor elements such as ICs and LSIs, similar members having fine patterns, such as liquid crystal elements and thin-film magnetic heads, and the like. In this process, exposure light from a mask having a predetermined circuit pattern and the like is projected on a photosensitive substrate such as a silicon wafer via a projection optical system to transfer the pattern formed on the mask onto the wafer.
As is apparent from the transition from the conventional ICs and LSIs to the current VLSIs and ULSIs, semiconductor integrated circuits have increased in integration degree. With this trend, projected patterns have been decreasing in size. Therefore, a higher resolution (resolving power) is required for projection optical systems and exposure apparatuses.